FAQ's

Q.What are the advantages of Electrostatic Loudspeakers (ESLs) over conventional magnetic speakers?

ESLs resolve all the subtle, inner-detail from music -- even at very low output levels. They have virtually zero distortion, so their sound quality is unbelievably clear and effortless. They produce a unified, coherent wave-front for precise, holographic-quality imaging. Because they have no high frequency resonances, their sound is very smooth and free from harshness or stridency.

They can do these things because unlike conventional magnetic speakers, they have essentially no moving mass. Their only moving part is a film of Mylar that is thinner than a human hair. This diaphragm has far less mass than the air it is driving, so it can start and stop instantly, which gives ESLs their terrific resolving power. An ESL is driven equally over its entire surface. So it cannot experience "cone breakup," which is the cause of speaker distortion.Because the mass of an ESL is far less than the air it drives, it is totally air-damped and cannot resonate at high frequencies. This is like trying to ring a bell underwater -- it just won't resonate. Because ESLs are panel speakers and are driven equally over their entire surface, the phase information they produce is coherent. This makes it possible for them to produce holographic images.

Q. How can ESLs reproduce so many octaves without crossovers?

The diaphragm material is extremely thin and sufficiently light in weight to reproduce frequencies well into the ultrasonic region. The electrostatic panel can be made large enough to move sufficient amounts of air in order to reproduce midrange and lower frequencies.

Q. If the electrostatic principle works so well for the reproduction of midrange and high frequencies, why use Transmission Line woofers ("T/Ls") to reproduce bass?

Electrostatic speakers can be designed to reproduce bass; however, they do so by sacrificing high Sound Pressure Levels (SPLs), "slam", linearity, and deep bass. Conventional magnetic woofers are quite capable in these areas -- if only their transient response and distortion can be controlled. The common closed box or vented enclosure fails to do so. However, T/Ls solve these problems and make it possible for a well-designed magnetic woofer to blend seamlessly with an ESL. This gives you the best of both worlds -- a speaker that is utterly clear with high output levels, and deep, powerful bass.

Q. Why do Sanders Sound Systems designs add the cost and complexity of electronic crossovers and biamplification when the majority of commercial products use one amplifier and passive crossovers that are much less costly?

There is an adage that says: "If something is worth doing, then it is worth doing well."

High performance audio is the personification of this belief. In the pursuit of excellence, using electronic crossovers is the means to far greater precision. Similarly, when an amplifier and woofer are directly connected, control of the driver is greatly improved.

Electronic crossovers can be made with much steeper crossover slopes of the exact shape desired. Unlike conventional passive, high-level crossovers, electronic crossovers cannot be overloaded.

Conventional crossovers not only require a single amplifier to drive several different drivers simultaneously, but they insert capacitors, inductors, and resistance between the amplifier and those drivers. This seriously hinders an amplifier's ability to control its drivers. With electronic crossovers, an amplifier operates only one driver, and it does so directly.

Q. Other manufacturers praise the use of a low crossover point in order to minimize the inherent problems crossovers present. Why do your products use higher frequencies?

Actually we don't. There is more to crossovers than just the crossover point. Understand that the woofer doesn't stop at the crossover point, its frequency response slowly declines beyond it. Most passive crossovers roll off at 12 dB/octave. Since the woofer's output must be at least 24 dB below that of the ESL before it can be considered to be out of the picture, the woofer will operate at least a couple of octaves above the crossover point in most speaker systems.

The selection of a crossover point involves many compromises having to do with the effect of dipole phase cancellation, clarity, equalization, output levels, and the woofer's ability to handle midrange frequencies. Sanders Sound Systems’ advanced Transmission Line woofers are able to operate flawlessly, well above the frequency range of most woofers. Crossover points and slopes are carefully selected to be sure that the woofers are operated within their capabilities as proven by the flawless integration for which our speakers are renowned.

It's true that Roger Sanders invented the free-standing, curved electrostatic panel in 1978. He published the technique in "Speaker Builder" magazine in 1980.

He expected that his wide-dispersion, curved panels would perform better than narrow-dispersion, planar speakers. But he was stunned to discover that they were inferior to planar speakers with respect to transient response, imaging, frequency response, speaker placement, and output!

Frustrated and disappointed, he spent several years studying these phenomena and eventually found that the laws of physics make it impossible for a wide-dispersion loudspeaker to have good transient response, imaging, etc. These topics are complex and technical, but the following explanation should help explain why this is true:

To visualize what happens, imagine that you have a conventional wide-dispersion loudspeaker that is perfect in every way. Now play a short transient through it, like a drum rim-shot. The sound that comes directly from the speaker to your ear is flawless (because we said the speaker was "perfect"). The transient is short, tight, and crisp. But because this hypothetical speaker has wide-dispersion, most of its sound goes out in the room where it reflects off various surfaces before reaching your ears. Because these reflected sounds must travel further than the direct sound to reach your ear, they arrive slightly later than the direct sound.

The delay is not enough for your brain to perceive them as echoes; instead you hear many rim-shots, over only a few milliseconds. So instead of hearing one crisp transient sound, you hear "pop corn" -- a group of transient sounds separated by tiny delays. Not knowing exactly what to do with this mess, your brain "averages" them all together into one, long, smeared transient sound.

If you doubt this, just remember the last time you heard headphones. No doubt you were impressed that the sound was far more clean and crisp than what you have heard from any wide-dispersion loudspeaker. This was not because the headphones were so good; it is just that headphones do not introduce room acoustics into the sound. Since music is almost all transient information, wide-dispersion speakers must be avoided if you want accurate sound.

Still another problem is frequency response. Because sound travels in waves, the out-of-phase room reflections will either augment or attenuate various frequencies when it mixes with the direct sound at your ear. This forms a "comb-filter", which seriously alters the accurate frequency response of our "perfect" speaker. Additionally, the room selectively absorbs the higher frequencies which tend to generally reduce the high frequency energy you hear in the overall sound when compared to the direct sound. The frequency response changes based on where the speaker is in the room; which is why speaker placement can be so difficult with wide-dispersion speakers. Finally, a wide-dispersion speaker expends most of its energy projecting its sound out in the room. A narrow-dispersion speaker directs most of its energy directly to you.

Although both speakers may produce identical amounts of sound output, the narrow-dispersion one will sound much louder, and therefore subjectively seems more efficient. In summary, wide-dispersion speakers force you to listen to your ROOM. Narrow-dispersion speakers allow you to listen to your SPEAKERS. The benefits of narrow-dispersion speakers are superior frequency response, higher output, holographic image quality, precision imaging, much crisper transients, and ease of placement.

Q. OK, I see the advantages of narrow dispersion, yet what happens when I leave the "sweet-spot?"

Sanders Sound Systems speakers are designed to bounce the ESL's rear-wave off the wall behind the speaker where it can spread out and fill the entire room. As a result, our speakers sound about the same off-axis as conventional, wide-dispersion speakers. When off-axis, you won't hear the precision image you do at the sweet-spot, however, the sound is quite satisfactory for casual listening or even for home-theater use.

Conventional wide-dispersion speakers have the same problem -- they can't produce a good image off-axis either. The laws of physics dictate that you must be equidistant from both speakers for your brain to have the accurate phase information needed to generate a 3-D image. Since wide-dispersion speakers can't produce a good image on-axis, it just isn't very obvious when you leave the sweet-spot.

Please understand that narrow-dispersion speakers don't sound worse than wide-dispersion ones when you move off-axis. Off-axis, both types sound about the same. It's that Sanders Sound Systems speakers sound so much BETTER than wide-dispersion speakers when you are in the sweet-spot.

Q. ESLs operate on very high voltages. How safe are they and will family members or pets be harmed by them?

There are two high voltage sources in an ESL that could cause a shock. The first is the static charge present on the diaphragm. You can't actually touch the diaphragm because it is guarded by the ultrastat panels. But even if a child were to stick something like a bobby pin, paper clip, or small screwdriver through the stator and touch the diaphragm, he/she wouldn't be injured because the diaphragm voltage is isolated by millions of ohms resistance. It cannot deliver enough current to cause damage. Being shocked by it is much like walking across a new carpet on a dry day and touching a doorknob. It's unpleasant, but harmless.

The other source of high voltage is the audio signal that is applied to the stators when music is playing loudly. This is a low impedance source of significant current that could be dangerous. However, the stators are covered with a proprietary high voltage insulation that is fully protective.

Q. How many watts are required to energize an electrostatic speaker?

Sanders Sound Systems ESLs are far more efficient than any other ESL, and more efficient than most magnetic speakers. A biamplified 10A has a sensitivity of about 94dB, and can be driven with low-power amplifiers.

Please keep in mind that no matter how good an amplifier is, if it is clipping, it will not sound clear and effortless. There is no substitute for lots of dynamic headroom. So, we recommend powerful amplifiers (at least 100 watts per channel). Also, "watts" is not an accurate way to measure amplifier performance when driving ESLs. Please see the section of our website that discusses our electrostatic amplifier for further details.

Q. What is the Difference between the old Innersound ESL amp and the new Sanders ESL amp?

The chassis is now aluminum.

All chassis parts are thicker to eliminate resonances.

XLR connectors are genuine Neutrik. They use professional metal sockets with locking devices.

RCA connectors are Cardas with Rhodium plating.

The power transformer is larger and more powerful. This has increased the amplifier's power from 300 watts to 360 watts/channel.

The power transformer is now fully shielded in an aluminum cylinder and potted in epoxy.

A new power supply circuit board is more compact and all wire has been eliminated (except for a 2" piece connecting the circuit board to the speaker binding post).

The amplifier is now completely modular in construction.

The face plate is "cleaner" and less cluttered.

The low-level, input amplifier circuitry has been redesigned to use the latest and best transistors.

The bias circuitry has been upgraded to provide more stable operation.

More powerful and linear output transistors are used to handle even more power and reduce distortion.

The new circuitry and transistors allow the use of less bias so that the amplifier runs even cooler than the original amp.

The speaker binding posts are placed at 45 degrees for ease of routing stiff speaker cables.

Both the ESL and Magtech amps use the same special amplifier modules that Roger designed to drive electrostatic speakers. The difference between the two is that ESL amps use a conventional, free-floating, unregulated power supply while Magtech amps use Roger's unique, 100% efficient, linear, regulated power supply.

Magnetic speakers draw tremendous current from an amplifier and that causes the internal power supply voltages to fluctuate dramatically in response to the music (typically by about 30%). This reduces the power from the amp and causes the distortion and bias to be modulated by the music.

A regulated power supply maintains stable internal voltages at all times. This is a tremendous improvement over a free-floating power supply. All amplifiers should use regulators, but virtually none do because their designers have not figured out how to make a powerful regulator that doesn't waste vast amounts of heat. Our regulator is unique in that it runs cold and wastes no heat. So we offer virtually the only regulated power supply amplifier on today's market.

Electrostatic speakers operate on voltage, not current. So they don't cause major fluctuations in the internal voltages like magnetic speakers do. But they will still cause some voltage modulation and mains voltage is not stable either. So even electrostatic speakers will benefit from an amplifier with a regulated power supply.

A regulated power supply will provide the best performance, so most of our customers (even our electrostatic speaker customers) opt for the Magtech. We keep the ESL amp in our line-up because it costs less than a Magtech and so represents a tremendous value. So those customers for whom money is a major concern, use the ESL amp instead of the Magtech.

In summary, the Magtech amp is the best for all speakers because it not only has the electrostatic amplifier modules, but it also includes a regulated power supply. So unless money is a major concern where the value of the ESL amp is essential, Roger recommends the Magtech.